1. Field of the Invention
This invention relates generally to endoscopes which provide for visualization of body cavities, openings, and conduits for surgical, diagnostic and therapeutic procedures.
2. Background of the Invention
An endoscope (sometimes referred to a "scope") is a device which is used to visualize body cavities, openings and conduits. This visualization is accomplished through light fibers which conduct light to the site of interest, and image fibers which return light images from the site being visualized. Typically endoscopes also include a working channel which permits the user to insert instruments which accomplish various operative functions, such as grasping, cutting and suturing, at the site being visualized. With these two purposes, visualization and operation, endoscopes are sometimes specifically configured to access a particular site and to perform a specific operative function at that site. These specialized scopes are sometimes referred to as cytoscopes, ureteroscopes, arthrascopes, laparoscopes, resectoscopes and the like.
An endoscope typically includes a housing which receives the fiberoptics and the surgical instruments from a location exterior of the patient, and a long narrow probe which extends from the housing to the operative site of interest. This probe may have an external diameter such as seven French and a length such as thirteen inches. The probe may be rigid, flexible, or semi-rigid depending primarily on the need to manipulate the tip of the probe through a torturous path. It is the configuration of this probe that is particular interest to the present invention.
The probes of the past have typically been cylindrical in configuration with an outer surface, and an inner surface defining a central lumen. In order to minimize trauma to the patient, it has always been of interest to decrease the cross-sectional circumference of the outer surface. This requirement has been directly opposed to the need to increase the cross-sectional circumference of the inner surface in order to maximize the size of the central lumen.
In a typical endoscope, the probe lumen may have a diameter of 0.089 inches. Within this diameter the central lumen must provide for a working channel having an outside diameter such as 0.050 inches, and a bundle of image fibers having a diameter such as 0.021 inches. Incident light fibers are generally much smaller in diameter and can be positioned in any of the remaining space not occupied by the working channel or the image bundle.
The conflict between the need to reduce the circumference of the outer surface and the need to increase the circumference of the inner surface of the probe has driven the technology to require a very thin wall for the probe. However, since the probe has a significant length to diameter ratio, the thin wall has made the probes highly susceptible to breaking. When one realizes that these probes are subjected to both torque and bending stresses as they are inserted through torturous paths, this tendency to break simply cannot be tolerated.
In order to reduce this risk of breaking, stress relief has been provided in the form of larger diameter, thicker walled tubes which have been disposed over the proximal end of the thin walled probe. This has tended to relieve the principal point of stress where the probe enters the housing. In some cases, several sleeves have been provided each with a reduced diameter in the distal direction. Unfortunately, in this configuration the sleeves tend to form shoulders on the outer surface of the probe. These shoulders also define points of significant bending stress, and additionally create a tendency for the outer surface of the probe to snag on various objects along the insertion path.